diff --git a/ghc/lib/std/cbits/system.c b/ghc/lib/std/cbits/system.c
index d4670bf9455dae03179c9aede15c05872efb2888..41bafd361fa6dd370a46801bbb124dafc5bae087 100644
--- a/ghc/lib/std/cbits/system.c
+++ b/ghc/lib/std/cbits/system.c
@@ -1,7 +1,7 @@
 /* 
  * (c) The GRASP/AQUA Project, Glasgow University, 1994-1998
  *
- * $Id: system.c,v 1.3 1998/12/02 13:27:59 simonm Exp $
+ * $Id: system.c,v 1.4 1999/01/07 15:42:33 simonm Exp $
  *
  * system Runtime Support
  */
@@ -9,6 +9,10 @@
 #include "Rts.h"
 #include "stgio.h"
 
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
 #ifdef HAVE_SYS_WAIT_H
 #include <sys/wait.h>
 #endif